There is considerable variation among patients in their ability to tolerate continuous-wear contact lenses. Although the lens may disturb several physiological functions, the minimum corneal oxygen requirement is probably the most important factor in limiting lens tolerance. I wish to determine the type and range of edematous corneal responses to continuous-wear hydrogel and other flexible contact lenses, and correlate these responses with the individual minimum oxygen requirement. Techniques will be developed for the more rapid measurement of the minimum oxygen requirement of the cornea which have potential clinical application. The experiments will consist of a series of pachometry measurements on each subject after exposure to low oxygen levels to establish the minimum corneal oxygen requirement. Then oxygen uptake will be determined by measurement with a polarographic oxygen electrode pressed against a contact lens while it is worn on the eye. In preliminary studies, this method was found to produce virtually no discomfort and has potential as a clinical testing procedure. Oxygen permeability of various test contact lenses will be measured and used to predict the edematous responses when the lenses are worn under continuous-wear conditions.